The reason why your hair has suddenly turned grey is…

Hair coloring might help temporarily solve going grey, but the underlying cause is likely due to stress, according to Harvard scientists.

Researchers from Harvard University discovered why prominent figures in time have suddenly had their hair turn white or gray. From Marie Antoinette’s hair allegedly turning white overnight as she awaited her fate during the French Revolution to the late Senator John McCain, who lost color in his hair after being a prisoner of war, researchers said extreme stress can start prematurely graying during the “fight-or-flight response,” which causes long-term, permanent damage to stem cells in hair follicles.

The study, published in the journal Nature, tested the theory on mice and found that graying started when the animals were forced to respond to danger.

“Everyone has an anecdote to share about how stress affects their body, particularly in their skin and hair — the only tissues we can see from the outside,” senior author Ya-Chieh Hsu, an associate professor of Stem Cell and Regenerative Biology at Harvard, said in a statement. “We wanted to understand if this connection is true, and if so, how stress leads to changes in diverse tissues. Hair pigmentation is such an accessible and tractable system to start with — and besides, we were genuinely curious to see if stress indeed leads to hair graying.”

In conjunction with researchers from the Center for Research on Inflammatory Diseases, the initial discovery happened when researchers were studying pain using black mice, where they administered resiniferatoxin in order to activate sensory nerve fibers and induce intense pain. Over the course of four weeks after the initial injection, one researcher found that the animals’ fur had turned completely white. Further tests found that the loss of melanocyte stem cells, which are found in hair follicles and determine hair color, during a stress-induced situation activates the “fight or flight” mentality.

“We set out to check the hypothesis that the loss of fur color resulted from pain-induced stress,” said Thiago Mattar Cunha, a researcher affiliated with the Center for Research on Inflammatory Diseases. “We designed a very simple experiment to see if the phenomenon was dependent on activation of sympathetic nerve fibers.”

Stem cells stop producing melanocytes as people age, thus when someone gets older, normally their hair can lose pigment and start turning grey. But in this study, they found that pain — or stress — actually started the aging of melanocytes stem cells earlier than predicted.

“In a young individual the cells are undifferentiated, like all stem cells, but with aging, they gradually differentiate. Once the process is complete they stop producing the melanocytes which produce melanin,” Cunha said. “We used various methodologies to show that intense sympathetic activity speeds up differentiation significantly. In our model, therefore, pain accelerated the aging of melanocyte stem cells.”

When these cells age prematurely, it spells for bad news: the damage is permanent, according to researchers.

Harvard researchers hope this study could lead to additional research that can “modify or block the damaging effects of stress.”

“By understanding precisely how stress affects stem cells that regenerate pigment, we’ve laid the groundwork for understanding how stress affects other tissues and organs in the body,” Hsu said. “Understanding how our tissues change under stress is the first critical step toward eventual treatment that can halt or revert the detrimental impact of stress. We still have a lot to learn in this area.”